webmail-client/frontend/src/routes/Login.tsx

import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
import { useState } from "react";
import { Link, useNavigate } from "react-router-dom";

import { useT } from "../i18n";
import { api, ApiError } from "../lib/api";

export function Login() {
  const t = useT();
  const [handle, setHandle] = useState("");
  const [password, setPassword] = useState("");
  const [totp, setTotp] = useState("");
  const [needTotp, setNeedTotp] = useState(false);
  const navigate = useNavigate();
  const queryClient = useQueryClient();
  // Only offer the signup link when the server would actually accept one.
  const registration = useQuery({ queryKey: ["registration"], queryFn: api.registrationStatus });

  const mutation = useMutation({
    mutationFn: () => api.login(handle, password, needTotp ? totp : undefined),
    onSuccess: (user) => {
      queryClient.setQueryData(["me"], user);
      navigate("/mail");
    },
    onError: (error) => {
      if (error instanceof ApiError && (error.code === "totp_required" || error.code === "totp_invalid")) {
        setNeedTotp(true);
      }
    },
  });

  const error = mutation.error instanceof ApiError ? mutation.error : null;
  // Don't show the "code required" error as a failure once we've revealed the field.
  const showError = error && !(needTotp && error.code === "totp_required");

  return (
    <div className="mx-auto mt-24 max-w-sm px-4">
      <h1 className="mb-6 text-2xl font-semibold">{t("auth.signInTitle")}</h1>
      <form
        className="space-y-3"
        onSubmit={(e) => {
          e.preventDefault();
          mutation.mutate();
        }}
      >
        <input
          className="w-full rounded-lg border border-app-border bg-app-surface px-3 py-2 text-app-fg placeholder:text-app-faint focus:border-app-accent focus:outline-none"
          placeholder={t("auth.handlePlaceholder")}
          value={handle}
          onChange={(e) => setHandle(e.target.value)}
          disabled={needTotp}
          autoFocus
        />
        <input
          className="w-full rounded-lg border border-app-border bg-app-surface px-3 py-2 text-app-fg placeholder:text-app-faint focus:border-app-accent focus:outline-none"
          type="password"
          placeholder={t("auth.password")}
          value={password}
          onChange={(e) => setPassword(e.target.value)}
          disabled={needTotp}
        />
        {needTotp && (
          <div className="space-y-1">
            <input
              className="w-full rounded-lg border border-app-border bg-app-surface px-3 py-2 text-app-fg placeholder:text-app-faint focus:border-app-accent focus:outline-none tracking-widest"
              placeholder="123456"
              inputMode="numeric"
              autoComplete="one-time-code"
              value={totp}
              onChange={(e) => setTotp(e.target.value)}
              autoFocus
            />
            <p className="text-xs text-app-muted">{t("auth.totpPrompt")}</p>
          </div>
        )}
        <button
          className="w-full rounded-lg bg-app-accent py-2 font-medium text-app-accent-fg hover:opacity-90 disabled:opacity-50"
          disabled={mutation.isPending}
          type="submit"
        >
          {mutation.isPending ? t("auth.signingIn") : t("auth.signIn")}
        </button>
        {showError && <p className="text-sm text-red-500">{error.message}</p>}
      </form>
      {registration.data?.open && (
        <p className="mt-4 text-sm text-app-muted">
          {t("auth.noAccount")}{" "}
          <Link className="text-app-accent" to="/register">
            {t("auth.register")}
          </Link>
        </p>
      )}
    </div>
  );
}